A light emitting structure of an Organic Light-Emitting Diode (OLED) device comprises a pair of electrode and an organic light-emitting layer. When a DC voltage is applied, holes are injected into the organic light-emitting layer from an anode, and electrons are injected into the organic light-emitting layer from a cathode. The electrons and holes are combined in the light-emitting layer and release energy, to excite molecules of an organic light-emitting material to form molecules in the excited state. When the molecules in the excited state return to the ground state, photons will be released to emit light.
An OLED display panel is fabricated in many ways, of which an OLED evaporation technology evaporates an organic light-emitting material and forms organic light-emitting devices on locations corresponding to pixels of an array substrate by using a Fine Metal Mask (FMM). Each pixel comprises red, green, and blue (R, G, B) sub-pixels; each sub-pixel has a shape of a quadrilateral, and each sub-pixel has a separate organic light emitting device.
Since an aperture area of the mask has a specified minimum limit, and influence from tolerance has to be considered during the fabrication procedure, enough gaps have to be left between apertures of adjacent pixels, which makes it impossible to improve pixel density significantly. Moreover, sub-pixels of different colors are made with different masks, so it is impossible to increase the arrangement density, the resolution cannot be increased accordingly. In the meantime, the evaporation has a shadow effect, which requires a space between two light-emitting regions, so as to prevent color-mixing. As a result, it is unlikely to make the openings on the mask smaller.